1. Field of the Invention
The present invention relates to an ultrasonic transducer assembly ("ultrasonic probe") used for an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic transducer assembly capable of acquiring three-dimensional echo data of a region within a living body to be examined.
2. Description of the Prior Art
An ultrasonic diagnostic apparatus electrically processes echo data acquired by transmitting and receiving ultrasonic waves to and from a region within a living body to be examined, and displays tomographic images and blood flow images and the like on the basis of the processed echo data. In the ultrasonic diagnostic apparatus, the ultrasonic waves are transmitted and received through an ultrasonic transducer assembly which is brought into contact with the body surface (e.g., a skin) of a patient to be examined. The ordinary ultrasonic transducer assembly is connected to a mainframe of the ultrasonic diagnostic apparatus via a cable for improvement of the movability and operatability of the transducer assembly. The ultrasonic waves are transmitted and received to and from a region within a patient to be examined with the use of an ultrasonic transducer provided in the transducer assembly.
In the conventional ultrasonic transducer assembly as described above, the ultrasonic transducer is fixedly disposed inside the transducer assembly. Therefore, whenever an diagnostic region, that is, a region from which echo data is acquired is required to change, it has been so far necessary to incline the ultrasonic transducer assembly which is in contact with the body surface of a patient to be examined by manual operation or with another mechanism prepared separately.
Recently, due to the advance of the image processing technology, there has been proposed an ultrasonic diagnostic apparatus capable of displaying three-dimensional ultrasonic images. In addition, an ultrasonic transducer assembly capable of acquiring three-dimensional echo data of a region within a patient to be examined has also been proposed (e.g., U.S. Pat. No. 5,152,294).
FIGS. 1 and 2 are schematical views showing the prior art ultrasonic transducer assemblies for acquiring three-dimensional echo data, in which FIG. 1 shows a typical example of the conventional ultrasonic transducer assembly, and FIG. 2 shows the ultrasonic transducer assembly disclosed in the above-mentioned U.S. Patent.
As shown in FIG. 1, the transducer assembly 8 includes a transducer unit 12 which is movably arranged within a casing 10 of the transducer assembly 8. This transducer unit 12 is adapted to be movable reciprocatingly in the right and left directions (the arrow directions A in FIG. 1) within the casing 10. The transducer unit 12 includes an array transducer (not shown) which is composed of a plurality of ultrasonic transducer elements. These transducer elements are arranged on a transmitting and receiving surface 12a of the transducer unit 12 which would, in use, face to a patient 14 to be examined.
Ultrasonic waves are transmitted from and received by the ultrasonic transducer elements in the direction roughly perpendicular to the transmitting and receiving surface 12a. Here, the respective ultrasonic transducer elements constituting the array transducer are arranged in the longitudinal direction of the transmitting and receiving surface 12a. Accordingly, it is possible to produce a scanning plane S1 (an area form which two-dimensional echo data can be obtained) by scanning the array transducer electronically. Further, under the condition, when the transducer unit 12 is moved mechanically for mechanical scanning in the right and left directions (the arrow directions A in FIG. 1), the electronic scanning plane S1 is also shifted. With this result, it is possible to acquire echo data of a three-dimensional region by shifting the electronic scanning plane S1 in the arrow directions A. In the case where the transducer assembly 8 as shown in FIG. 1 is used for ultrasonic diagnosis, the three-dimensional echo data acquiring region is formed in such a way that the plane S2 along which the electronic scanning plane S1 is shifted by mechanical scanning (hereinafter, referred to "as mechanical scanning plane") becomes a rectangular shape.
On the other hand, with respect to the transducer assembly 16 shown in FIG. 2, a transducer unit 18 including an array transducer (not shown) composed of a plurality of ultrasonic transducer elements is swung mechanically for mechanical scanning in the arrow directions A within a casing 10. In accordance with this transducer assembly 16, the electronic scanning plane S1 can be produced by electronically scanning the array transducer. In addition, the three-dimensional echo data acquiring region can be formed in such a way that the mechanical scanning plane S2 becomes roughly trapezoidal when the transducer unit 18 is swung mechanically.
As described above, when the transducer assembly 8 or 16 as shown in FIG. 1 or 2 is used for the ultrasonic diagnosis, it is possible to acquire the three-dimensional echo data of a region in a patient to be examined simply and accurately, without moving the casing 10 of the transducer assembly by manual operation or with another mechanism provided separately.
In the above-mentioned prior art transducer assemblies 8 and 16, however, there is a problem in that it is difficult to acquire echo data, depending on the parts or regions to be diagnosed.
For instance, when the transducer assembly is brought into contact with breast of a patient to be examined in order to diagnose a heart thereof, shade portions 102 are inevitably produced on the back side of the ribs 100 as shown in the drawing since the ribs transmit less ultrasonic waves. In other words, since reflected echo cut off by the ribs 100 can not be received by the transducer, the acquired echo data is not complete and noise is liable to be generated, thus raising a serious problem in that the displayed three-dimensional ultrasonic images are indistinct. Therefore, the prior art ultrasonic transducer assemblies could not be used in the diagnosis for a heart.